DE112013006340T5 - Cutting tool and cutting insert with exactly three cutting sections for it - Google Patents

Abstract

In a cutting tool having an indexable cutting insert (20) with three cutting sections (26), the cutting insert is removably attachable to an insert holder (52) by means of a fixture (54). The cutting insert has two opposite end surfaces (22) with a peripheral side surface (24) extending therebetween. At least one end surface has a central hub (36) projecting therefrom with a raised support surface (38), and the peripheral side surface has three abutment recesses (28). In an end view of the cutting insert, each of the three abutment recesses is visible and within a first imaginary circle (C1) that circumscribes the visible center hub. A holding portion of the insert holder has a seat surface (58) with at least one projecting protrusion (60a, 60b). The support surface is in clamping contact with the seat, and exactly two of the three plant recesses are engaged with the at least one protrusion.

Description

Field of the invention

The invention relates to metal cutting tools for use in grooving and grooving operations having an indexable cutting insert with a plurality of cutting sections.

Background of the invention

In the field of metal cutting tools used in grooving and grooving operations, cutting inserts which are removably mountable in an insert holder have long provided a means of cutting with a suitably hard material, i. h. carbide, in the vicinity of the cutting edge, wherein the insert holder made of a less hard material is reusable after disposal of a worn or damaged cutting insert.

This type of cutting tool has been further developed to use indexable inserts with an increased number of cutting edges, providing economic benefits since a greater number of cutting operations are performed per cutting insert. In addition, this type of cutting tool has been developed to provide a more efficient means for securing the turnover insert to the insert holder.

The US-A-4461602 discloses a milling cutter which consists of a shank, a milling cutter plate and a bolt, by means of which the milling cutter plate is detachably fastened to the front end of the shank. The latter has a recess in its front surface. The recess is defined by three planar side surfaces leaving a circumferential gap between each pair thereof. The substantially triangular shaped cutter plate is fitted in the recess so that it is immovable in a radial plane. Bulges of the cutter plate protrude through the gaps and are each provided with a cutting edge.

The US-A-5607263 discloses an insert having a disc-shaped body with three teeth and a single integrally formed projection. The holder has a front surface recess which is completely surrounded by a wall of the holder. According to 5 and 6 of the US-A-5607263 the projection has a coupling surface with the contour of a triangular convex polygon, and the recess has a mating surface with the contour of a triangular concave polygon, and in a charged state, three contact zones are formed between the coupling surface and the mating surface.

It is an object of the invention to provide an improved indexable cutting insert and an improved cutting tool.

Another object of the invention is to enable the cutting insert to be stably fixed to a mating body with efficient use of space.

Another object of the invention is to provide a cutting insert which is suitable both for left-handed and for right-handed cutting tools.

Yet another object of the invention is to provide a cutting tool with good support for the acting cutting portion.

An additional object of the invention is to provide a cutting tool that can perform internal piercing operations with cutting depths that amount to at least a quarter of the bore diameter of the workpiece in which the holding portion extends.

Summary of the invention

According to the invention, there is provided an indexable cutting insert comprising: two opposite end surfaces having a peripheral side surface and a central axis extending therebetween,
a median plane lying between the two opposite end faces,
exactly three cutting sections, each cutting section having a main cutting edge extending from one end surface to the other end surface,
exactly three investment recesses in the peripheral page area and
a central hub projecting from at least one of the two opposing end surfaces,
each center hub having an elevated support surface axially further away from the median plane than any point on the three major cutting edges located on the same side of the median plane, and
wherein, in an end view of the cutting insert, each of the three abutment recesses is visible and lies within a first imaginary circle circumscribing the center hub.

Further, according to the present invention, there is provided a cutting tool having an insert holder and at least one cutting insert of the type described above retained therein.

The insert holder has a holding portion extending along a longitudinal tool axis, wherein the holding portion has a seat surface transversely to the longitudinal tool axis with at least one protrusion protruding from the seat,
wherein the at least one cutting insert is removably securable by means of attachment to the insert holder,
wherein exactly one cutting section of each cutting insert is operative,
wherein a support surface of each cutting insert is in clamping contact with the seating surface and
wherein exactly two of the three abutment recesses of each cutting insert are engaged with the at least one protrusion.

Brief description of the drawings

For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which dotted lines represent truncated boundaries for partial views of a component. Show it:

1 a perspective view of a cutting insert according to some embodiments of the invention;

2 an end view of the cutting insert according to 1 ;

3 a cross-sectional view of the cutting insert according to 2 on the line III-III;

4 a cross-sectional view of the cutting insert according to 3 on the IV-IV line;

5 a detailed view of the cutting insert according to 3 ;

6 an exploded perspective view of a cutting tool according to some embodiments of the invention;

7 an end view of the cutting tool according to 6 with the attachment removed;

8th a perspective view of an insert holder according to some embodiments of the invention; and

9 an end view of the insert holder according to 8th ,

Further description of the invention

First up 1 to 5 referenced, which is an indexable insert 20 obtained by compression molding and sintering a cemented carbide, z. B. Woframcarbid, may be prepared and may be coated or uncoated.

According to the invention, the cutting insert 20 two opposite end surfaces 22 with a peripheral side surface 24 and a center axis A1 extending therebetween, and exactly three cutting sections 26 ,

In some embodiments of the invention, the cutting insert 20 be reversible about the center axis A1.

According to the invention, the peripheral side surface 24 exactly three investment savings 28 , and each of the three cutting sections 26 has a main cutting edge 30 extending from an end face 22 to the other end surface 22 extends.

In some embodiments of the invention, according to 1 and 4 each of the three main cutting edges 30 by cutting a rake surface 32 and an open space 34 be formed, and the chip and open space 32 . 34 can on the peripheral side surface 24 lie.

In addition, in some embodiments of the invention, the three cutting sections 26 around the center axis A1 alternating with the three plant recesses 28 be equally spaced over the circumference.

Further, in some embodiments of the invention, the three cutting sections 26 over the circumference and from the three investment recesses 28 be radially spaced.

Furthermore, in some embodiments of the invention, all three cutting sections 26 be identical.

In addition, in some embodiments of the invention, all three plant recesses 28 be identical.

It should be understood that the use of the terms "radial" and "axial" throughout the specification and claims means the positioning of elements of the cutting insert 20 with respect to the center axis A1.

According to 2 can the cutting insert 20 Show rotational symmetry about the central axis A1.

In some embodiments of the invention, according to 2 each of the three cutting sections 26 have a radial plane P1 having the central axis A1 and a first point N1 on its respective major cutting edge 30 contains.

In addition, in some embodiments of the invention according to 2 each radial plane P1 has an acute internal clearance angle α with an imaginary one Freeraden L _C form, leading to the open space 34 immediately adjacent to their respective first point N1 is tangent, and the acute clearance angle α may have a value of at least 75 degrees, ie, α ≥ 75 °.

By the cutting insert 20 is configured so that it has clearance angle α of at least 75 degrees, is advantageously a robust support for the acting cutting edge 30 provided in the course of Inneneinstechvorgängen.

It should be noted that the use of the terms "inner angle" and "outer angle" throughout the specification and claims refers to an angle between two planar and / or rectilinear components in the measurement inside and outside the component on which these components are respectively formed.

According to the invention according to 3 and 5 the cutting insert 20 a median plane M, which is between the two opposite end faces 22 lies, and a middle hub 36 that is from at least one of the two opposite end faces 22 protrudes. Every midsection 36 has a raised support surface 38 axially further away from median plane M than any point on the three major cutting edges 30 lying on the same side of the median plane M.

The cutting insert 20 with raised support surfaces 38 to configure, advantageously allows a modification of the three cutting sections 26 to several product variants without modification of the support surfaces 38 to achieve.

In some embodiments of the present invention, each of the three cutting sections 26 from the at least one central hub 36 be radially spaced.

Furthermore, in some embodiments of the invention according to FIG 2 every midsection 36 have three second points N2 included in the three radial planes P1, and every other point N2 can be at the shortest distance between its respective center hub 36 and its respective first point N1.

In addition, in some embodiments of the invention according to 2 every second point N2 on a curved section 76 his respective middle hub 36 lie, and each curved section 36 may be outwardly convex in relation to the central axis A1.

Every curved section 76 so as to be outwardly convex in relation to the central axis A1, it is advantageously possible to optimize cutting depths of internal piercing operations.

In addition, in some embodiments of the invention, each of the three cutting sections 26 two minor cutting edges 40 have, with each secondary cutting edge 40 away from its associated main cutting edge 30 extends toward the median plane M.

According to 3 and 5 can both end surfaces 22 a middle hub 36 have, so the cutting insert 20 a total of two middle hives 36 Has.

In some embodiments of the invention, according to 3 each support surface 38 be substantially planar and perpendicular to the central axis A1.

Each support surface 38 to be configured so that it is flat and perpendicular to the center axis A1, advantageously facilitates the accurate and repeatable turning of the cutting insert 20 ,

In addition, in some embodiments of the invention according to 3 and 5 each support surface 38 the axially outermost surface of its associated end surface 22 be.

According to 3 the median plane M can be perpendicular to the central axis A1.

In some embodiments of the present invention, the median plane M may be the perimeter side surface 24 along the entire perimeter of the peripheral side surface 24 to cut.

In addition, in some embodiments of the present invention according to FIG 3 the cutting insert 20 Mirror symmetry to the median plane M show. In such embodiments, the cutting insert is 20 reversible and can be advantageous for both left and right-handed cutting tools.

According to the invention, in an end view of the cutting insert 20 according to 2 each of the three investment savings 28 visible and lies at least partially within a first imaginary circle C1, which is the visible central hub 36 rewrites. The first imaginary circle C1 has a first diameter D1.

The cutting insert 20 with three investment recesses 28 configuring within the first imaginary circle C1 advantageously allows the cutting insert 20 to attach stably to a counter-body with efficient use of space.

In some embodiments of the invention, each of the three plant recesses 28 in both end views of the cutting insert 20 being visible.

In addition, in some embodiments of the invention, each of the three abutment recesses 28 every midsection 36 to cut.

In alternative embodiments of the invention (not shown), each center hub may have three spaced protrusions with coplanar support faces.

According to 2 can the three main cutting edges 30 define a second imaginary circle C2 having a second diameter D2 that defines the peripheral side surface 24 rewrites.

In some embodiments of the invention, the center of the second imaginary circle C2 may coincide with the center axis A1.

Further, in some embodiments of the invention, the first diameter D1 may be at most two-thirds of the second diameter D2, i. h., D1 ≤ 2 / 3D2.

In addition, in some embodiments of the present invention, each curved portion 76 have a radius which is at most as large as the radius of the second imaginary circle C2.

By the radius of each curved section 76 is configured so that it is at most as large as the radius of the second imaginary circle C2, advantageously cutting depths of Inneneinstechvorgängen be optimized in holes with small diameters.

In an end view of the cutting insert 20 can according to 2 a third imaginary circle C3 the visible central hub 36 and exactly two of the three cutting sections 26 contain.

In some embodiments of the invention, the second and third imaginary circles C2, C3 may have the same second diameter D2, and an offset distance O between the centers of the second and third imaginary circles C2, C3 may be at least a quarter of their second diameter D2, i. h., O ≥ D2 / 4.

In an end view of the cutting insert 20 can according to 2 and 4 each of the three investment savings 28 a pair of spaced contact surfaces 44a . 44b have that form a V-shape.

In some embodiments of the present invention, each pair of contact surfaces 44a . 44b through a curved connection surface 46 be spaced, and each connection surface 46 may be the radially innermost point of their associated plant recess 28 contain.

Furthermore, in some embodiments of the present invention, any abutment surface 44a . 44b an imaginary straight line L _A parallel to the center axis A1 included.

Furthermore, in some embodiments of the invention, any abutment surface 44a . 44b be substantially planar, and in a cross section of the cutting insert 20 in a plane perpendicular to the central axis A1 can according to 4 every pair of contact surfaces 44a . 44b form an outer recess angle β having a value between 60 and 120 degrees, ie, 60 ° <β <120 °.

In addition, in some embodiments of the invention, the recess angle β between each pair of abutment surfaces 44a . 44b a value between 60 and 120 degrees in each cross section of the cutting insert 20 in a plane perpendicular to the center axis A1.

In some embodiments of the invention, each endface 22 a deeper area 48 have, extending from each of the three cutting sections 26 extends radially inward.

According to 5 can any deeper area 48 axially closer to the median plane M than a portion of the main cutting edge 30 their associated cutting section 26 lie.

Furthermore, according to 5 every deeper area 48 be substantially planar and perpendicular to the center axis A1, and each deeper surface 48 can define a deeper plane P2, which is the main cutting edge 30 their associated cutting section 26 cuts.

Now be on 6 and 7 referenced, which is a cutting tool according to the invention 50 Show that an insert holder 52 and at least one cutting insert 20 having.

The at least one cutting insert 20 is at the insert holder 52 with the help of a fastening 54 removably attached.

According to 8th and 9 has the insert owner 52 a holding section 56 which extends along a longitudinal tool axis A2, and the holding portion 56 has a seat 58 transverse to the longitudinal tool axis A2 with at least one protrusion 60a . 60b from the seat 58 protrudes.

In some embodiments of the invention, the seat surface 58 be substantially planar and perpendicular to the longitudinal tool axis A2.

According to the invention is according to 7 exactly one cutting section 26 every cutting insert 20 acting, a support surface 38 every cutting insert 20 is in clamping contact with the seat 58 , and exactly two of the three investment savings 28 every cutting insert 20 stand with the at least one protrusion 60a . 60b engaged.

In some embodiments of the present invention, according to 7 exactly two spaced corner sections 42a . 42b the at least one protrusion 60a . 60b within the first imaginary circle C1 of each cutting insert 20 lie.

Furthermore, in some embodiments of the present invention according to FIG 2 and 7 every cutting insert 20 a center hole 62 have, which extends coaxially with its central axis A1.

Additionally, in some embodiments of the present invention, the center bore 62 in both end views of the cutting insert 20 being visible.

Furthermore, in some embodiments of the present invention according to FIG 6 the attachment 54 the shape of a clamping screw 64 have, extending through the cutting center hole 62 extends and an engagement with a threaded hole 66 in the seat 58 of the holding section 56 manufactures.

According to 7 can the rake surfaces 32 every cutting insert 20 generally facing the central axis A1 in a first circumferential direction d1, and the exact two abutment recesses 28 every cutting insert 20 engaged with the at least one protrusion 60a . 60b can stand the first and second next investment savings 28a . 28b to her acting cutting section 26a in an opposite second circumferential direction d2 about its central axis A1. In addition, the next investment savings remains 28c in the first circumferential direction d1 about the central axis A1 without engagement.

The cutting tool 50 to configure so that the first next plant recess 28a to her acting cutting section 26a in the second circumferential direction d2 engagement with the at least one protrusion 60a . 60b produces, can advantageously the acting cutting section 26a support and absorb cutting forces during operation.

In some embodiments of the present invention, both abutment surfaces 44a . 44b in association with the first investment cut-off 28a to her acting cutting section 26a in the second circumferential direction d2 in clamping contact with the at least one protrusion 60a . 60b stand, and only one of the contact surfaces 44a in allocation to the second nearest investment recess 28b to her acting cutting section 26a in the second circumferential direction d2 can be in clamping contact with the at least one protrusion 60a . 60b stand.

Further, in some embodiments of the present invention, the two abutment surfaces 44a . 44b in association with the first investment cut-off 28a to her acting cutting section 26a in the second circumferential direction d2 in clamping contact with a respective first and second reaction or counter pressure wall 68 . 70 the at least one protrusion 60a . 60b stand, and the single contact surface 44a in allocation to the second nearest investment recess 28b to her acting cutting section 26a in the second circumferential direction d2 may be in clamping contact with a corresponding third counter-pressure wall 72 the at least one protrusion 60a . 60b stand, and each of the first, second and third counter-pressure wall 68 . 70 . 72 may include an imaginary back pressure line L _R parallel to the longitudinal tool axis A2.

According to 7 can the single investment area 44a in clamping contact with the third counter-pressure wall 72 generally point in the second circumferential direction d2 about its central axis A1.

In some embodiments of the present invention, each threaded hole 66 in relation to their respective center hole 62 be off-center. In such embodiments, the tightening of the clamping screw presses 64 in their threaded hole 66 every cutting insert 20 in the transverse direction with respect to the longitudinal tool axis A2, which clamping contact between three of its contact surfaces 44a . 44b and three corresponding back pressure walls 68 . 70 . 72 guaranteed.

Furthermore, in some embodiments of the present invention according to FIG 6 and 7 exactly one cutting insert 20 on the insert holder 52 be attached, exactly two spaced protrusions 60a . 60b can from the seat 58 protrude, and the first and second counter-pressure wall 68 . 70 can on a first protrusion 60a lie, and the third counter-pressure wall 72 may be on a second protrusion 60b lie. In such embodiments, the first protrusion 60a a first corner section 42a , and the second protrusion 60b has a second corner section 42b ,

The insert holder 52 with exactly two spaced protrusions 60a . 60b to configure, advantageously, the individual cutting insert 20 on the insert holder 52 to secure with efficient use of space.

In some embodiments of the present invention with exactly one cutting insert 20 , the stakeholder 52 is attached, the holding section 56 be elongated and extending from a shaft section 74 extend along longitudinally.

In an end view of the cutting tool 50 according to 7 the second imaginary circle C2 may be the entire holding section 56 contain.

In addition, in an end view of the cutting tool 50 according to 7 the third imaginary circle C3 the entire holding section 56 contain.

Since the offset distance O between the centers of the second and third imaginary circle C2, C3 can be at least a quarter of its second diameter D2, ie, O ≥ D2 / 4, the cutting tool 50 advantageously be used to perform Inneneinstechvorgänge with cutting depths that amount to at least a quarter of the bore diameter of the workpiece in which the holding section 56 extends.

In alternative embodiments of the present invention (not shown), the cutting tool may have a plurality of cutting inserts removably attached to the seating surface of the insert holder, and the cutting tool may be rotatable about the longitudinal tool axis and used in slot milling operations.

Although the invention has been particularly described to some extent, it should be understood that various changes and modifications could be made without departing from the spirit or scope of the invention as claimed in the following claims.

Claims (47)

Indexable insert ( 20 ), comprising: two opposite end surfaces ( 22 ) having a peripheral side surface ( 24 ) and a central axis (A1) extending therebetween, a median plane (M) lying between the two opposite end surfaces (FIG. 22 ), exactly three cutting sections ( 26 ), each cutting section ( 26 ) a main cutting edge ( 30 ) extending from an end face ( 22 ) to the other end surface ( 22 ), exactly three investment savings ( 28 ) in the peripheral side surface ( 24 ) and a central hub ( 36 ) of at least one of the two opposite end surfaces ( 22 ), each center hub ( 36 ) an increased support surface ( 38 ) located axially further from the median plane (M) than any point on the three major cutting edges (FIG. 30 ) lying on the same side of the median plane (M) and in an end view of the cutting insert (FIG. 20 ) each of the three investment savings ( 28 ) is visible and lies within a first imaginary circle (C1) which is the central hub (C1) 36 ). Cutting insert ( 20 ) according to claim 1, wherein each support surface ( 38 ) is substantially planar and perpendicular to the central axis (A1). Cutting insert ( 20 ) according to claim 1 or 2, wherein each of the three plant recesses ( 28 ) every central hub ( 36 ) cuts. Cutting insert ( 20 ) according to any one of the preceding claims, wherein each support surface ( 38 ) the axially outermost surface of its associated end surface ( 22 ). Cutting insert ( 20 ) according to one of the preceding claims, wherein in both end views of the cutting insert ( 20 ) each of the three investment savings ( 28 ) is visible. Cutting insert ( 20 ) according to any one of the preceding claims, wherein each of the three plant recesses ( 28 ) a pair of spaced contact surfaces ( 44a . 44b ) which has a V-shape in an end view of the cutting insert ( 20 ) form. Cutting insert ( 20 ) according to claim 6, wherein each pair of contact surfaces ( 44a . 44b ) by a curved connection surface ( 46 ) and wherein each bonding surface ( 46 ) the radially innermost point of their associated plant recess ( 28 ) contains. Cutting insert ( 20 ) according to claim 6 or 7, wherein each abutment surface ( 44a . 44b ) contains an imaginary straight line (L _A ) parallel to the central axis (A1). Cutting insert ( 20 ) according to one of claims 6 to 8, wherein each contact surface ( 44a . 44b ) is substantially planar, wherein in a cross-section of the cutting insert ( 20 ) in a plane perpendicular to the central axis (A1) of each pair of contact surfaces ( 44a . 44b ) forms an outer recess angle (β) and the recess angle (β) has a value between 60 and 120 degrees. Cutting insert ( 20 ) according to one of the preceding claims, wherein the median plane (M) covers the peripheral side surface ( 24 ) along the entire perimeter of the peripheral side surface ( 24 ) cuts. Cutting insert ( 20 ) according to one of the preceding claims, wherein the median plane (M) is perpendicular to the central axis (A1). Cutting insert ( 20 ) according to one of the preceding claims, wherein the cutting insert ( 20 ) is reversible about the central axis (A1). Cutting insert ( 20 ) according to one of the preceding claims, wherein the cutting insert ( 20 ) Shows mirror symmetry to the median plane (M). Cutting insert ( 20 ) according to one of the preceding claims, wherein the three main cutting edges ( 30 ) define a second imaginary circle (C2) having a second diameter (D2) defining the peripheral side surface (D2). 24 ). Cutting insert ( 20 ) according to claim 14, wherein the center of the second imaginary circle (C2) coincides with the central axis (A1). Cutting insert ( 20 ) according to claim 14 or 15, wherein the first imaginary circle (C1) has a first diameter (D1) and wherein the first diameter (D1) is at most two thirds of the second diameter (D2). Cutting insert ( 20 ) according to one of claims 14 to 16, wherein in an end view of the cutting insert ( 20 ) a third imaginary circle (C3) the visible central hub (C3) 36 ) and exactly two of the three cutting sections ( 26 ), wherein the second and third imaginary circles (C2, C3) have the same second diameter (D2) and wherein an offset distance (O) between the centers of the second and third imaginary circle (C2, C3) is at least a quarter of its second diameter (D2) is. Cutting insert ( 20 ) according to one of the preceding claims, wherein each of the three cutting sections ( 26 ) has a radial plane (P1) having the central axis (A1) and a first point (N1) on its respective major cutting edge (P1) 30 ), and wherein each central hub ( 36 ) has three second points (N2) contained in the three radial planes (P1) and every other point (N2) in the shortest distance between its respective central hub (N2) 36 ) and its respective first point (N1). Cutting insert ( 20 ) according to claim 18, wherein every other point (N2) on a curved section ( 76 ) of its respective central hub ( 36 ) and wherein each curved section ( 76 ) is outwardly convex relative to the central axis (A1). Cutting insert ( 20 ) according to claim 19, wherein the three main cutting edges ( 30 ) define a second imaginary circle (C2) defining the peripheral side surface (C2) 24 ), and wherein each curved section ( 76 ) has a radius which is at most as large as the radius of the second imaginary circle (C2). Cutting insert ( 20 ) according to one of the preceding claims, wherein each of the three main cutting edges ( 30 ) by cutting a chip surface ( 32 ) and an open space ( 34 ) and wherein the chip and free surface ( 32 . 34 ) on the peripheral side surface ( 24 ) lie. Cutting insert ( 20 ) according to claim 21, wherein each of the three cutting sections ( 26 ) has a radial plane (P1) having the central axis (A1) and a first point (N1) on its respective major cutting edge (P1) 30 ), wherein each radial plane (P1) forms an acute internal clearance angle (α) with an imaginary freerad (L _C ) facing the open space ( 34 ) is tangential immediately adjacent to its respective first point (N1), and wherein the acute clearance angle (α) has a value of at least 75 degrees. Cutting insert ( 20 ) according to claim 21 or 22, wherein each deeper surface ( 48 axially closer to the median plane (M) than a portion of the main cutting edge (FIG. 30 ) of its associated cutting section ( 26 ) lies. Cutting insert ( 20 ) according to any one of claims 21 to 23, wherein each deeper surface ( 48 ) is substantially planar and perpendicular to the central axis (A1), and wherein each deeper surface ( 48 ) defines a deeper plane (P2) that defines the main cutting edge (P2) 30 ) of its associated cutting section ( 26 ) cuts. Cutting insert ( 20 ) according to one of the preceding claims, wherein each of the three cutting sections ( 26 ) from the at least one central hub ( 36 ) is radially spaced. Cutting insert ( 20 ) according to any one of the preceding claims, wherein each end face ( 22 ) a deeper surface ( 48 ) extending from each of the three cutting sections ( 26 ) extends radially inwardly. Cutting insert ( 20 ) according to one of the preceding claims, wherein the three cutting sections ( 26 ) over the circumference and of the three plant recesses ( 28 ) are radially spaced. Cutting insert ( 20 ) according to one of the preceding claims, wherein the three cutting sections ( 26 ) about the central axis (A1) alternately with the three plant recesses (A1) 28 ) are equally spaced over the circumference. Cutting insert ( 20 ) according to one of the preceding claims, wherein all three cutting sections ( 26 ) are identical. Cutting insert ( 20 ) according to any one of the preceding claims, wherein all three plant recesses ( 28 ) are identical. Cutting insert ( 20 ) according to one of the preceding claims, wherein the cutting insert ( 20 ) Shows rotational symmetry about the central axis (A1). Cutting insert ( 20 ) according to one of the preceding claims, wherein a central bore ( 62 ) extends coaxially with the central axis (A1). Cutting insert ( 20 ) according to claim 32, wherein the central bore ( 62 ) in both end views of the cutting insert ( 20 ) is visible. Cutting tool ( 50 ), an insert holder ( 52 ) and at least one cutting insert ( 20 ) according to any one of the preceding claims, which is retained therein. Cutting tool ( 50 ) according to claim 34, wherein: the insert holder ( 52 ) a holding section ( 56 ) which extends along a longitudinal tool axis (A2), wherein the holding portion ( 56 ) a seat ( 58 ) transversely to the longitudinal tool axis (A2) with at least one protrusion ( 60a . 60b ), from the seat ( 58 ) projecting at least one cutting insert ( 20 ) by means of a fastening ( 54 ) on the insert holder ( 52 ) is removably attachable, wherein exactly one cutting section ( 26 ) of each cutting insert ( 20 ), wherein a support surface ( 38 ) of each cutting insert ( 20 ) in clamping contact with the seat surface ( 58 ) and where exactly two of the three investment savings ( 28 ) of each cutting insert ( 20 ) in engagement with the at least one protrusion ( 60a . 60b ) stand. Cutting tool ( 50 ) according to claim 35, wherein exactly two spaced-apart corner sections ( 42a . 42b ) of the at least one protrusion ( 60a . 60b ) within the first imaginary circle (C1) of each cutting insert ( 20 ) lie. Cutting tool ( 50 ) according to claim 35 or 36, wherein each of the three cutting sections ( 26 ) of each cutting insert ( 20 ) a chip surface ( 32 ), which points generally in a first circumferential direction (d1) about the central axis (A1), and wherein the exactly two abutment recesses ( 28 ) of each cutting insert ( 20 ) engaged with the at least one protrusion ( 60a . 60b ), the first and second succeeding investment savings ( 28a . 28b ) to the acting cutting insert cutting section (FIG. 26a ) in an opposite second circumferential direction (d2) about its central axis (A1). Cutting tool ( 50 ) according to claim 37, wherein each of the three plant recesses ( 28 ) of each cutting insert ( 20 ) a pair of spaced contact surfaces ( 44a . 44b ) which has a V-shape in an end view of each cutting insert ( 20 ), both abutment surfaces ( 44a . 44b ) in association with the first investment cut-off ( 28a ) to its acting cutting section ( 26a ) in the second circumferential direction (d2) in clamping contact with the at least one protrusion ( 60a . 60b ) and only one of the contact surfaces ( 44a ) in association with the second closest investment savings ( 28b ) to its acting cutting section ( 26a ) in the second circumferential direction (d2) in clamping contact with the at least one protrusion ( 60a . 60b ) stands. Cutting tool ( 50 ) according to claim 38, wherein the two contact surfaces ( 44a . 44b ) in association with the first investment cut-off ( 28a ) to its acting cutting section ( 26a ) in the second circumferential direction (d2) in clamping contact with a corresponding first and second counter-pressure wall ( 68 . 70 ) of the at least one protrusion ( 60a . 60b ), wherein the individual contact surface ( 44a ) in association with the second closest investment savings ( 28b ) to its acting cutting section ( 26a ) in the second circumferential direction (d2) in clamping contact with a corresponding third counter-pressure wall ( 72 ) of the at least one protrusion ( 60a . 60b ) and wherein each of the first, second and third counter-pressure wall ( 68 . 70 . 72 ) contains an imaginary back pressure straight line (L _R ) parallel to the longitudinal tool axis (A2). Cutting tool ( 50 ) according to claim 39, wherein the single contact surface ( 44a ) in clamping contact with the third counter-pressure wall ( 72 ) generally in the second circumferential direction (d2) about its central axis (A1). Cutting tool ( 50 ) according to claim 39 or 40, wherein exactly one cutting insert ( 20 ) on the insert holder ( 52 ), wherein exactly two spaced protrusions ( 60a . 60b ) from the seat ( 58 ) and wherein the first and second counter-pressure wall ( 68 . 70 ) on a first protrusion ( 60a ) and the third counter-pressure wall ( 72 ) on a second protrusion ( 60b ) lies. Cutting tool ( 50 ) according to one of claims 35 to 41, wherein the seat surface ( 58 ) is substantially planar and perpendicular to the longitudinal tool axis (A2). Cutting tool ( 50 ) according to one of claims 35 to 42, wherein each cutting insert ( 20 ) a central bore ( 62 ), which extends coaxially with its central axis (A1), and wherein the attachment ( 54 ) the shape of a clamping screw ( 64 ), which extends through the cutting center hole ( 62 ) extends and an engagement with a threaded hole ( 66 ) in the seat ( 58 ) of the holding section ( 56 ). Cutting tool ( 50 ) according to claim 43, wherein each threaded hole ( 66 ) in relation to their respective center hole ( 62 ) is off-center. Cutting tool ( 50 ) according to one of claims 35 to 44, wherein exactly one cutting insert ( 20 ) on the insert holder ( 52 ) and wherein the three main cutting edges ( 30 ) define a second imaginary circle (C2) having a second diameter (D2) defining its peripheral side surface (D2). 24 ). Cutting tool ( 50 ) according to claim 45, wherein the holding section ( 56 ) is elongated and extending from a shank portion ( 74 ) extends longitudinally and wherein in an end view of the cutting tool ( 50 ) the second imaginary circle (C2) the entire holding section ( 56 ) contains. Cutting tool ( 50 ) according to claim 46, wherein in an end view of the cutting tool ( 50 ) a third imaginary circle (C3) the entire holding section ( 56 and wherein the second and third imaginary circles (C2, C3) have the same second diameter (D2) and an offset distance (O) between the centers of the second and third imaginary circles (C2, C3) is at least one fourth of their second diameter ( D2) is.

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